1. Field of the Invention
The present invention relates to a wired circuit board and a producing method thereof and, more particularly, to a wired circuit board used appropriately for a suspension board with circuit which is mounted in a hard disk drive and a producing method thereof.
2. Description of the Related Art
A suspension board with circuit is obtained by successively laminating an insulating base layer, a conductive layer having terminal portions, and an insulating cover layer on a metal supporting layer, and then trimming the metal supporting layer.
Such a suspension board with circuit is typically mounted in a hard disk drive after a magnetic head is positioned using a reference hole formed in a metal supporting layer as a reference, and mounted in the suspension board with circuit.
In recent years, the terminals of a magnetic head and the terminal portions of a suspension board with circuit have been configured at a finer pitch, so that it is necessary to increase the reliability of connection therebetween. Therefore, it is needed to form the reference hole with high accuracy to improve the accuracy of positioning of the magnetic head.
To satisfy the need, a method has been proposed in which, e.g., a material more resistant to etching than stainless steel, such as zirconium or palladium, is stuck to a surface of a suspension board made of stainless steel, and then the suspension board is etched to form reference holes (see, e.g., Japanese Unexamined Patent No. 2005-217250). In the etching step of Japanese Unexamined Patent No. 2005-217250, the reference holes are bored such that the inner end surfaces of the suspension board (the inner circumferential surfaces of the reference holes) are uniformly etched due to the above-mentioned material stuck to the suspension board to improve the accuracy of processing of the reference holes.